Added support to use pkg shlib-{provides,requires} objects.

This effectively checks that all pkgs in a transaction to be installed
or updated, have not unmatched shared libraries, which might happen with
pkgs that had major soname bumps.

This implementation slow downs xbps_transaction_prepare() 2x, due to
the use of xbps_pkgdb_get_pkg_metadata(). A new pkgdb format is required
that adds the pkg shlib-provides objects to pkgdb, avoiding the need
to use xbps_pkgdb_get_pkg_metadata().

lib/Makefile

@@ -36,7 +36,7 @@ EXTOBJS = external/dewey.o external/fexec.o external/mkpath.o
 OBJS = package_configure.o package_config_files.o package_orphans.o
 OBJS += package_remove.o package_find_obsoletes.o package_state.o
 OBJS += package_unpack.o package_register.o package_script.o verifysig.o
-OBJS += package_msg.o
+OBJS += package_msg.o transaction_shlibs.o
 OBJS += transaction_commit.o transaction_package_replace.o
 OBJS += transaction_dictionary.o transaction_sortdeps.o transaction_ops.o
 OBJS += transaction_revdeps.o pubkey2fp.o